1. Field of the Invention
The present invention relates to a method and circuit for sampling input waveform signals at a predetermined periodic rate and detecting a peak point and a bottom point in each sampling period.
2. Description of the Prior Art
As known hitherto, a prior art sampling method includes, as shown in FIG. 7, comparing a sampling value obtained immediately before the beginning of a sampling period with the sampling period peak and bottom values to determine which value has the greatest difference from the sampling value during the period of sampling. The value which is output corresponds to the peak or bottom value which results in the greatest difference from the sampling value.
According to this method and referring to this FIG. 7, no problem may be encountered at sampling points t.sub.1 to t.sub.4 where the difference value to a peak level is less than that to a bottom level within each sampling period. However, despite a peak arising between t.sub.5 and t.sub.6, the peak level L.sub.P will not be output since the difference from the sampled value is greater to bottom level L.sub.B. Accordingly, where, for example, QRS wave of an electrocardiogram signal is sampled, a peak value when the sampling value is reproduced sharply fluctuates as compared with an input waveform despite the peak level being almost uniform.